The topside equatorial ionosphere during daytime: Elevated plasma temperatures,the transequatorial O⁺ breeze and the dynamics of minor ions     

G.I. Bailey  R.I. Moffett 《Planetary and Space Science》1979,27(8):1075-1085

Steady-state calculations are performed for the daytime equatorial F2-region and topside ionosphere. Values are calculated of the electron and ion temperatures and the concentrations and field-aligned velocities of the ions O⁺, H⁺ and He⁺. Account is taken of upward $\text{E × B}$ drift, a summer-winter horizontal neutral air wind and heating of the electron gas by thermalization of fast photoelectrons.The calculated plasma temperatures are in accord with experiment: at the equator there is an isothermal region from about 400–550 km altitude, with temperatures of about 2400 K around 800 km altitude. The transequatorial O⁺ breeze flux from summer to winter in the topside ionosphere is not greatly affected by the elevated plasma temperatures. The field-aligned velocities of H⁺ and He⁺ depend strongly on the O⁺ field-aligned velocity and on the presence of large temperature gradients. For the minor ions, ion-ion drag with O⁺ cannot be neglected for the topside ionosphere.  相似文献   

Ion transition heights from topside electron density profiles     

J.E. Titheridge 《Planetary and Space Science》1976,24(3):229-245

Theoretical electron density profiles are calculated for the topside ionosphere to determine the major factors controlling the profile shape. Only the mean temperature, the vertical temperature gradient and the $\text{O}{}^{\mathrm{+}}\text{H}{}^{\mathrm{+}}$ ion transition height are important. Vertical proton fluxes alter the ion transition height but have no other effect on the profile shape. Diffusive equilibrium profiles including only these three effects fit observed profiles, at all latitudes, to within experimental accuracy.Values of plasma temperature, temperature gradient and ion transition height h_tT were determined by fitting theoretical models to 60,000 experimental profiles obtained from Alouette l ionograms, at latitudes of 75°S–85°N near solar minimum. Inside the plasmasphere h_T varies from about 500 km on winter nights to 850 km on summer days. Diurnal variations are caused primarily by the production and loss of O⁺ in the ionosphere. The approximately constant winter night value of h_T is close to the level for chemical equilibrium. In summer h_T is always above the equilibrium level, giving a continual production of protons which travel along lines of force to aid in maintaining the conjugate winter night ionosphere. Outside the plasmasphere h_T is 300–600 km above the equilibrium level at all times. This implies a continual near-limiting upwards flux of protons which persists down to latitudes of about 60° at night and 50° during the day.  相似文献   

Deuteron whistler and trans-equatorial propagation of the ion cyclotron whistler     

S. Watanabe  T. Ondoh 《Planetary and Space Science》1976,24(4):359-364

New ion cyclotron whistlers which have the asymptotic frequency of one half the local proton gyrofrequency, $\text{G}{}_{\mathrm{p}}\text{2}$, and the minimum (or equatorial) proton gyrofrequency, G_pm, along the geomagnetic field line passing through the satellite have been found in the low-latitude topside ionosphere from the spectrum analysis of ISIS VLF electric field data received at Kashima, Japan. Ion cyclotron whistlers with asymptotic frequency of G_pm or $\text{G}{}_{\mathrm{pm}}\text{2}$ are observed only in the region of $\text{B}{}_{\mathrm{m}}\text{>}\text{B}\text{2}$ or rarely $\text{B}{}_{\mathrm{m}}\text{>}\text{B}\text{4}$, where B is the local magnetic field and B_m is the mini magnetic field along the geomagnetic field line passing through the satellite.The particles with one half the proton gyrofrequency may be the deuteron or alpha particle. Theoretical spectrograms of the electron whistlers (R-mode) and the ion cyclotron whistlers (L-mode) propagating along the geomagnetic field lines are computed for the appropriate distributions of the electron density and the ionic composition, and compared with the observed spectrograms.The result shows that the ion cyclotron whistler with the asymptotic frequency of $\text{G}{}_{\mathrm{p}}\text{2}$ is the deuteron whistler, and that the ion cyclotron whistlers with the asymptotic frequency of G_pm or $\text{G}{}_{\mathrm{pm}}\text{2}$ are caused by the trans-equatorial propagation of the proton or deuteron whistler from the other hemisphere.  相似文献   

Thermal proton flow in the plasmasphere: The morning sector     

Peter M. Banks  Joe R. Doupnik 《Planetary and Space Science》1974,22(1):79-94

Vertical profiles of electron density obtained in the vicinity of the plasmapause using the Alouette-II topside sounder have been analyzed to assess the presence of H⁺ flow in the topside ionosphere. The observations in the midnight sector show clearly the presence of the plasmapause; i.e. there is a sharp boundary separating the poleward regions of polar wind H⁺ flow and the more gentle conditions of the plasmasphere where light ions are present in abundance. In contrast, in the sunlit morning sector upwards H⁺ flow is deduced to be present to invariant latitudes as low as 48° (L = 2·2) in the regions normally known to be well inside the plasmasphere. The upwards H⁺ flux is sufficiently large (3 × 10⁸ ions cm^?2 sec^?1) that the plasmapause cannot be seen in the latitudinal electron density contours of the topside ionosphere. The cause for this flow remains unknown but it may be a result of a diurnal refilling process.  相似文献   

Plasma temperatures from alouette 1 electron density profiles     

J.E. Titheridge 《Planetary and Space Science》1976,24(3):247-259

Values of plasma temperature and vertical temperature gradient were obtained by fitting theoretical models to 60,000 observed electron density profiles, at heights of 400–1000 km. Results show the diurnal and seasonal changes in temperature from 75°S to 85°N near solar minimum. At night the temperature and temperature gradient are both low inside the plasmapause and high outside. Day-time temperatures increase almost linearly with latitude, from 1500 K at the magnetic equator to a maximum of 3500 K at the plasmapause. There is also a sharp peak at 77° latitude, beneath the magnetospheric cleft. Mean vertical temperature gradients are $\text{ca. 0.5}\text{K}\text{km}$ at night, and 1–4 K/km during the day. The downwards flow of heat, during the day, increases from about zero at 10° latitude to a maximum of $\text{4 × 10}{}^9\text{eV}\text{cm}{}^2\text{sec}$ at the plasmapause. Night-time flows are 5–20 times less, inside the plasmasphere. Increases in magnetic activity cause a temperature increase at 400 km, of about 70 K per unit increase in K_p at all latitudes greater than 65°. The temperature peaks at the plasmapause and the magnetospheric cleft show little increase with magnetic activity, but move equatorwards by ca. 2° in latitude per unit K_p.  相似文献   

The calculated and observed diurnal variation of the ionosphere over Millstone Hill on 23–24 March 1970     

R.G. Roble 《Planetary and Space Science》1975,23(7):1017-1033

A numerical model of current F-region theory is use to calculate the diurnal variation of the mid-latitude ionospheric F-region over Millstone Hill on 23–24 March 1970, during quiet geomagnetic conditions. From the solar EUV flux, the model calculates at each altitude and time step primary photoelectron spectra and ionization rates of various ion species. The photoelectron transport equation is solved for the secondary ionization rates, photoelectron spectra, and various airglow excitation rates. Five ion continuity equations that include the effects of transport by diffusion, magnetospheric-ionospheric plasma transport, electric fields, and neutral winds are solved for the ion composition and electron density. The electron and ion temperatures are also calculated using the heating rates determined from chemical reactions, photoelectron collisions, and magnetospheric-ionospheric energy transport. The calculations are performed for a diurnal cycle considering a stationary field tube co-rotating with the Earth; only the vertical plasma drift caused by electric fields perpendicular to the geomagnetic field line is allowed but not the horizontal drift. The boundary conditions used in the model are determined from the incoherent scatter radar measurements of T_e, T_i and O⁺ flux at 800km over Millstone Hill (Evans, 1971a). The component of the neutral thermospheric winds along the geomagnetic field has an important influence on the overall ionospheric structure. It is determined from a separate dynamic model of the neutral thermosphere, using incoherent scatter radar measurements.The calculated diurnal variation of the ionospheric structure agrees well with the values measured by the incoherent scatter radar when certain restrictions are placed on the solar EUV flux and model neutral atmospheric compositions. Namely, the solar EUV fluxes of Hinteregger (1970) are doubled and an atomic oxygen concentration of at least $\text{10}{}^{11}\text{cm}{}^3$ at 120 km is required for the neutral model atmosphere. Calculations also show that the topside thermal structure of the ionosphere is primarily maintained by a flow of heat from the magnetosphere and the night-time F2-region is maintained in part by neutral winds, diffusion, electric fields, and plasma flow from the magnetosphere. The problem of maintaining the calculated night-time ionosphere at the observed values is also discussed.  相似文献   

Thermal response properties of the Earth's ionospheric plasma     

R.G. Roble  J.T. Hastings 《Planetary and Space Science》1977,25(3):217-231

The thermal response of the Earth's ionospheric plasma is calculated for various suddenly applied electron and ion heat sources. The time-dependent coupled electron and ion energy equations are solved by a semi-automatic computational scheme that employs Newton's method for coupled vector systems of non-linear parabolic (second order) partial differential equations in one spatial dimension. First, the electron and composite ion energy equations along a geomagnetic field line are solved with respect to a variety of ionospheric heat sources that include: thermal conduction in the daytime ionosphere; heating by electric fields acting perpendicular to the geomagnetic field line; and heating within a stable auroral red are (SAR-arc). The energy equations are then extended to resolve differential temperature profiles, first for two separate ion species (H⁺, O⁺) and then for four separate ion species (H⁺, He⁺, N⁺, O⁺) in addition to the electron temperature. The electron and individual ion temperatures are calculated for conditions within a night-time SAR-arc excited by heat flowing from the magnetosphere into the ionosphere, and also for typical midlatitude daytime ionospheric conditions. It is shown that in the lower ionosphere all ion species have the same temperature; however, in the topside ionosphere above about 400 km, ion species can display differential temperatures depending upon the balance between thermal conduction, heating by collision with electrons, cooling by collisions with the neutrals, and energy transfer by inter-ion collisions. Both the time evolution and steady-state distribution of such ion temperature differentials are discussed.The results show that below 300km both the electrons and ions respond rapidly (<30s) to variations in direct thermal forcing. Above 600 km the electrons and ions display quite different times to reach steady state, depending on the electron density: when the electron density is low the electrons reach steady state temperatures in 30 s, but typically require 700 s when the density is high; the ions, on the other hand, reach steady state in 700 s when the density is high, and 1500–2500 s when the density is low. Between 300 and 600 km, a variety of thermal structures can exist, depending upon the electron density and the type of thermal forcing; however steady state is generally reached in 200–1000 s.  相似文献   

The transient response of the topside ionosphere to precipitation   总被引：1，自引：0，他引：1  

J.H. Whitteker 《Planetary and Space Science》1977,25(8):773-786

A numerical time-dependent model of the topside and F-layer ionosphere is used to describe how the density of O⁺ ions and the plasma temperatures change as a result of transient electron precipitation with a soft energy spectrum (ca. 100 eV per electron). The response time for electron gas heating is about 2 min; for changes in topside scale height it is from 5 to 15 min, depending on altitude; and for changes in F-layer peak density, it is more than an hour. The low-density topside ion gas is thermally isolated on a short time scale; consequently the ion temperature responds almost adiabatically to volume changes. A transient precipitation event (of, say, 10 min duration) initiates a disturbance that propagates upward at approximately the sonic upeed in the plasma (ca. 2km/s), growing in amplitude with height. Such an event has little effect on the density at the peak of the F layer. An element of ionosphere that drifts horizontally in an antisunward direction through the magnetospheric cleft and into the polar cap recieves some ionization from the cleft, but not enough to be decisive in its survival. The collapse of the topside when heating is removed increases temporarily the density of the F layer.  相似文献   

Plasma bubbles near the dawn terminator in the topside ionosphere     

William I. Burke 《Planetary and Space Science》1979,27(9):1187-1193

The physical properties of plasma bubbles in the topside ionosphere near the dawn terminator are investigated. It is assumed that the bubbles result from either a Rayleigh-Taylor or an $\text{E}\text{×}\text{B}$ instability on the bottom side of the F-layer. While the E-region is in darkness, the top and bottomsides of the ionosphere are electrically decoupled and the motion of bubbles can be described by non-linear, two-dimensional theory. After sunrise, electric fields within the bubbles discharge through the conducting lower ionosphere. The upward drift of the bubbles is effectively halted. To achieve a dayside state of diffusive equilibrium the bubbles slowly begin to collapse from the bottom.  相似文献   

Effect of diffusion-thermal processes on the high-latitude topside ionosphere     

R.W. Schunk  W.J. Raitt  A.F. Nagy 《Planetary and Space Science》1978,26(2):189-191

We have studied the extent to which diffusion-thermal heat flow affects H⁺ temperatures in the high-latitude topside ionosphere. Such a heat flow occurs whenever there are H⁺?O⁺ relative drifts. From our study we have found that at high-latitudes, where H⁺ flows up and out of the topside ionosphere, diffusion-thermal heat flow acts to reduce H⁺ temperatures by 500–600 K at altitudes above about 900 km.  相似文献   

A two-dimensional model of the ionosphere of Venus: Thermal structure     

《Icarus》1986,67(2):325-335

A two-dimensional spectral model of energetics in the ionosphere of Venus has been constructed. The effects of horizontal bulk transport of heat and the heat flux saturation have been taken into account. The model is capable of explaining the observed high ion temperatures for solar zenith angles greater than 140°. An external heat input to ions of 1–2 × 10⁻⁴ergs cm⁻²sec⁻¹ almost uniformly distributed over the entire planet gives good agreement with the average ion temperature data from the PVO retarding potential analyzer. The effects of varying the magnitude of the horizontal plasma velocity, including the vertical component of bulk velocity, changing the altitude dependence of the velocity profile, and making the ionopause height a function of solar zenith angle have been discussed.  相似文献   

Infrared properties of haze particles of Venus     

Sonoyo Mukai  Tadashi Mukai 《Icarus》1981,48(3):482-487

The computed variation of the infrared flux and polarization of Venus as a function of phase angle, based upon multiple-scattering calculations for the cloud model of Kawabata et al. (1980) with an internal heat source, precludes the possibility of sulfuric acid as the composition of the haze particles located above the main cloud. Furthermore, our calculations reveal that the hazticle should have a large absorption coefficient at these wavelengths, i.e, $\text{k(}\text{imaginary part of the complex refractive index}\text{) ? 1.3}\text{at a wavelength}\text{λ = 3.4 μ}\text{m}$. The optical thickness of the haze layer must be about 0.15 at λ = 3.4 μm.  相似文献   

Small-scale turbulence in the atmosphere of Venus     

Richard Woo  J.W. Armstrong  A.J. Kliore 《Icarus》1982,52(2):335-345

Previous studies based on radio scintillation measurements of the atmosphere of Venus have identified two regions of small-scale temperature fluctuations located in the vicinity of 45 and 60 km. A global study of the fluctuations near 60 km, which are consistent with wind-shear-generated turbulence, was conducted using the Pioneer Venus measurements. The structure constants of refractive index fluctuations c_n² and temperature fluctuations c_T² increase poleward, peak near 70° latitude, and decrease over the pole; c_n² varies from 2 × 10^?15 to 1.5 × 10^?14m^{$\text{2}\text{3}$} and c_T² from 4 × 10^?3 to 7 × 10^?2°K²m^{$\text{?2}\text{3}$}. These results indicate greater turbulent activity at the higher latitudes. In the region near 45 km the refractive index fluctuations and the corresponding temperature fluctuations are substantially lower. Based on the analysis of one representative occultation measurement, $\text{c}{}_{\mathrm{<mtext>n</mtext>}}{}^2\text{= 2 × 10}{}^{\mathrm{?16}}\text{m}{}^{\mathrm{<mtext>?2</mtext><mtext>3</mtext>}}\text{and}\text{c}{}_{\mathrm{<mtext>T</mtext>}}{}^2\text{= 7.3 × 10}{}^{\mathrm{?4}}\text{°}\text{K}{}^2\text{m}{}^{\mathrm{<mtext>?2</mtext><mtext>3</mtext>}}$ in the 45-km region. The fluctuations in this region also appear to be consistent with wind-shear-generated turbulence. The turbulence level is considerably weaker than that at 60 km; the energy dissipation rate ε is 4.9 × 10^?5m²sec^?3 and the small-scale eddy diffusion coefficient K is 2 × 10³ cm² sec^?1.  相似文献   

Diffusion coefficients for three major ions in the topside ionosphere     

S. Quegan  G.J. Bailey  R.J. Moffett 《Planetary and Space Science》1981,29(8):851-867

Published experimental data on ion composition in the topside ionosphere are examined. For certain features (the light ion trough, the high-latitude trough, the high-latitude hole and the mid-latitude total ion concentration trough) it is pointed out that the number of major ions present may be 3 or more. Transport equations derived by Schunk and co-workers are extended to include the case of three major ions in the topside ionosphere. Specific calculations are made for the O⁺, H⁺ and He⁺ ions and the behaviour of the diffusion coefficients is discussed. From a model of the high-latitude ionization hole, described by Heelis et al., representative concentration and temperature profiles are obtained. These profiles are used to demonstrate further the behaviour of the ion diffusion coefficients.  相似文献   

Deuterium on Venus: Model comparisons with pioneer Venus observations of the predawn bulge ionosphere     

Shailendra Kumar  Harry A. Taylor 《Icarus》1985,62(3):494-504

A model of the predawn bulge ionosphere composition and structure is constructed and compared with the ion mass spectrometer measurements from the Pioneer Venus Orbiter during orbits 117 and 120. Particular emphasis is given to the identification of the mass-2 ion which we find unequivocally due to D⁺ (and not H₂⁺). The atmospheric D/H ratio of 1.4% and 2.5% is obtained at the homopause (～ 130 km) for the two orbits. The H₂⁺ contribution to the mass-2 ion density is less than 10%, and the H₂ mixing ratio must be <0.1 ppm at 130 km altitude. The He⁺ data require a downward He⁺ flux of ～2 × 10⁷ cm^?2 sec^?1 in the predawn region which suggest that the light ions also flow across the terminator from day to night along with the observed O⁺ ion flow.  相似文献   

Topside ionosphere disturbance effects during different phases of two successive magnetic storms in september, 1963     

M.N. Fatkullin 《Planetary and Space Science》1972

Using the data obtained by means of the Alouette-1 satellite, the distribution of electron density in the region of the F2-layer maximum and topside ionosphere during different phases of two successive magnetic storms on September 13 and 16,1963 have been studied. The middle latitudes at local near noon and midnight hours have been considered mainly. It is shown that the daytime topside electron density at some altitudes did not change during the main phases of the two magnetic storms. The electron density decreases below these levels and increases above. During the recovery phases of both magnetic storms the increase in electron density remains at all altitudes from h_mF2 to 1000 km.  相似文献   

Diffusion and heat flow equations for the mid-latitude topside ionosphere     

J.-P. St.-Maurice  R.W. Schunk 《Planetary and Space Science》1977,25(10):907-920

For application to the mid-latitude topside ionosphere, we have derived diffusion and heat flow equations for a gas mixture composed of two major ions, electrons and a number of minor ions. These equations were derived by expanding the velocity distribution of each constituent about its 13 lower order velocity moments. As a consequence, each constituent was allowed to have its own temperature and drift velocity. The restriction to mid-latitudes results because we have assumed that the species temperature and drift velocity differences were small. In deriving the diffusion and thermal conduction equations, we have discovered some new transport effects. For the major ions, we have found that: (1) a temperature gradient in either gas causes thermal diffusion in both gases; (2) a temperature gradient in either gas causes heat to flow in both gases; and (3) a relative drift between the major ion gases induces a heat flow in both gases. Similar transport effects have also been found for the minor ions.  相似文献   

PL whistlers     

R.J. Thomson 《Planetary and Space Science》1977,25(11):1037-1043

Simultaneous ground and satellite VLF observations together with raytracing studies clearly establishes the existence of ground observed PL whistlers. The dynamic spectrum $\text{(?-ν-t}\text{shape}\text{)}$ of observed PL whistlers may be reproduced exactly by raytracing in TLG magnetospheric models consistent with lower ionosphere, topside ionosphere and equatorial density measurements. The Transition Level Gradient (TLG) model is based on the observation that the transition level altitude increases towards the plasmapause (Titheridge, 1976). PL ground whistlers (i) are observed downgoing over large latitudinal ranges, for up to 2000 km of satellite travel, by ISIS II at 1400 km altitude, (ii) have almost the same dynamic spectrum over the entire latitudinal range observed by ISIS II, (iii) are indistinguishable from ducted whistlers over the observed frequency range (i.e. linear Q for ? < 10 kHz), (iv) have nose frequencies > 16 kHz, (v) at 1400 km altitude have a lower latitudinal cutoff at L ～ 2 and a higher latitudinal cutoff between L ～ 3 and L ～ 4 and (vi) probably only occur at night-time during or immediately following disturbed magnetic activity.  相似文献   

Transterminator ion flow in the Martian ionosphere     

M. Fränz  E. Dubinin  J. Woch  R. Lundin 《Planetary and Space Science》2010,58(11):1442-1454

The upper ionospheres of Mars and Venus are permeated by the magnetic fields induced by the solar wind. It is a long-standing question whether these fields can put the dense ionospheric plasma into motion. If so, the transterminator flow of the upper ionosphere could explain a significant part of the ion escape from the planets atmospheres. But it has been technically very challenging to measure the ion flow at energies below 20 eV. The only such measurements have been made by the ORPA instrument of the Pioneer Venus Orbiter reporting speeds of 1-5 km/s for O⁺ ions at Venus above 300 km altitude at the terminator ( [Knudsen et al., 1980] and [Knudsen et al., 1982]). At Venus the transterminator flow is sufficient to sustain a permanent nightside ionosphere, at Mars a nightside ionosphere is observed only sporadically. We here report on new measurements of the transterminator ion flow at Mars by the ASPERA-3 experiment on board Mars Express with support from the MARSIS radar experiment for some orbits with fortunate observation geometry. We observe a transterminator flow of O⁺ and O₂⁺ ions with a super-sonic velocity of around 5 km/s and fluxes of 0.8×10⁹/cm² s. If we assume a symmetric flux around the terminator this corresponds to an ion flow of 3.1±0.5×10²⁵/s half of which is expected to escape from the planet. This escape flux is significantly higher than previously observed on the tailside of Mars. A possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime. We discuss the implication of these new observations for ion escape and possible extensions of the analysis to dayside observations which may allow us to infer the flow structure imposed by the induced magnetic field.  相似文献   

Airborne spectroscopy and spacecraft radiometry of Venus in the far infrared     

H.H. Aumann  J.V. Martonchik  G.S. Orton 《Icarus》1982,49(2):227-243

In March 1979, the spectrum of Venus was recorded in the far infrared from the G.P. Kuiper Airborne Observatory when the planet subtended a phase angle of 62°. The brightness temperature was observed to be 275°K near 110 cm^?1, dropping to 230°K near 270 cm^?1. Radiance calculations, using temperature and cloud structure formation from the Pioneer Venus mission and including gaseous absorption by the collision-induced dipole of CO₂, yield results consistently brighter than the observations. Supplementing the spectral data, Pioneer Venus OIR data at similar phase angles provide the constraint that any additional infrared opacity must be contained in the upper cloud, H₂SO₄ to the Pioneer-measured upper cloud structure serves to reconcile the model spectrum and the observations, but cloud microphysics strongly indicates that such a high particle density haze $\text{(N ? 1.6 × 10}{}^7\text{cm}{}^{\mathrm{?3}}\text{)}$ is implausible. The atmospheric environment is reviewed with regard to the far infrared opacity and possible particle distribution modifications are discussed. We conclude that the most likely possibility for supplementing the far-infrared opacity is a population of large particles $\text{(}\text{r}\text{? 1 μm)}$ in the upper cloud with number densities less than 1 particle cm^?3 which has remained undetected by in situ measurements.  相似文献